1. Field of the Invention
The present invention relates to a method of fabricating a micro-vertical structure and, more specifically, to a method of fabricating a micro-vertical structure with a planar vertical surface without causing morphological defects or footings.
2. Discussion of Related Art
Micro-electro-mechanical systems (MEMS) refers to the integration of mechanical elements, sensors, actuators, and electronic circuits on a common silicon (Si) substrate through microfabrication technology. MEMS is being applied in a wide range of fields including sensors, actuators, and micro-machines.
In general, fabricating a MEMS device involves forming a micro-vertical structure by etching a Si substrate using a deep reactive ion etching (DRIE) technique.
However, when the Si substrate is etched using the DRIE technique, morphological defects, scallops, microloading effect, and footings may occur on the Si substrate. This will now be described in more detail with reference to FIGS. 1A through 1C.
FIGS. 1A through 1C are diagrams for explaining the problems of morphological defects, scallops, etch retardation, and footings caused to a Si substrate etched using a DRIE technique.
Referring to FIG. 1A, when the Si substrate is etched using a DRIE technique, morphological defects, such as parallel deviation 11 or spherical deviation 12, may be caused or scallops 13 may occur, causing roughening of the etched vertical surface.
Referring to FIG. 1B, microloading effect 14 and 15 may occur such that a large-area space is etched faster than a small-area space. Referring to FIG. 1C, footings 16 may occur due to reactive ions generated during the etching process such that an etch end-point is etched excessively.
As described above, when a Si substrate is etched using a DRIE technique, etched vertical surfaces are seriously damaged due to morphological defects, scallops, microloading effect, and footings, thereby adversely affecting the performances of MEMS devices using micro-vertical structures, such as sensors, optical switches, and optical filters.
In addition, after a DRIE process is performed, a micro-vertical structure floats and thus, it is difficult to perform subsequent processes, such as a dicing process.